Vertical difference, which measures distance between estimated and actual cost for every single observation is classified as

The correct answer is A. residual term.

A residual term is the difference between an observed value and the value predicted by a model. In the case of a cost function, the residual term is the difference between the actual cost and the estimated cost.

A positive term is a term in an equation that is greater than zero. A negative term is a term in an equation that is less than zero. A squared term is a term in an equation that is the square of another term.

In the case of a cost function, the residual term is not a positive term, a negative term, or a squared term. It is simply the difference between the actual cost and the estimated cost.